C#根据年月日算出是星期几

  /// <summary>
    /// 基姆拉尔森计算公式计算日期
    /// </summary>
    /// <param name="y">年</param>
    /// <param name="m">月</param>
    /// <param name="d">日</param>
    /// <returns>星期几</returns>
   
   protected string CaculateWeekDay(int y, int m, int d)
    {
        if (m == 1 || m == 2)
        {
            m += 12;
  //把一月和二月看成是上一年的十三月和十四月，例：如果是2004-1-10则换算成：2003-13-10来代入公式计算。
            y--;       
        }
        int week = (d + 2 * m + 3 * (m + 1) / 5 + y + y / 4 - y / 100 + y / 400) % 7;
        string weekstr = "";
        switch (week)
        {
            case 0: weekstr = "星期一"; break;
            case 1: weekstr = "星期二"; break;
            case 2: weekstr = "星期三"; break;
            case 3: weekstr = "星期四"; break;
            case 4: weekstr = "星期五"; break;
            case 5: weekstr = "星期六"; break;
            case 6: weekstr = "星期日"; break;
        }
        return weekstr;
    }